ES6 Javascript繼承

Question

提供了以下代碼：

class Person { 
    constructor(name) { 
     this.name = name; 
    } 
    sayHello() { 
     console.log('Hello, my name is ' + this.name); 
    } 
    sayHelloAndBy() { 
     this.sayHello(); 
     console.log('Bye'); 
    } 

} 
class Student extends Person { 
    constructor(name, grade) { 
     super(name); 
     this.grade = grade; 
    } 
    sayHello() { 
     console.log(`Hi, I'm a studend and my name is ` + this.name); 
    } 
} 


let b = new Student("Some guy", 5); 

b.sayHelloAndBy(); 

我想弄清楚調用sayHello在Person在Student定義，而不是一個辦法。可能嗎 ？

在php中有self::允許一個這樣做，但我不知道JS是否有類似的概念。

Answer 1

你可以參考版本的sayHello通過Person的原型財產Person定義，並把它用Function#call必要this：

sayHelloAndBye() { 
    Person.prototype.sayHello.call(this); 
    console.log('Bye'); 
} 

的Runnable：

class Person { 
 
    constructor(name) { 
 
     this.name = name; 
 
    } 
 
    
 
    sayHello() { 
 
     console.log('Hello, my name is ' + this.name); 
 
    } 
 
    
 
    sayHelloAndBye() { 
 
     Person.prototype.sayHello.call(this); 
 
     console.log('Bye'); 
 
    } 
 
} 
 

 
class Student extends Person { 
 
    constructor(name, grade) { 
 
     super(name); 
 
     this.grade = grade; 
 
    } 
 
    sayHello() { 
 
     console.log(`Hi, I'm a studend and my name is ` + this.name); 
 
    } 
 
} 
 

 
let b = new Student("Some guy", 5); 
 

 
b.sayHelloAndBye();